Right, left or moderate
This includes friends and in particular, family members. It would seem intuitive that siblings brought up together, by the same parents, would likely have similar views. And while in my family, I think that's largely true, there are areas of distinct disagreement. My point here is I can't help but think the same must be true among members of all political persuasions, only more so.
A good example is our old friend, Senator Harry Reid. Like most in his party, he generally votes with the left, but he is an ardent defender of the Second Amendment, unlike the vast majority of statists. There is the the question though, of whether this is due to his true feelings or simply another political decision based on the state he represents (Nevada) and the strong pro-gun sentiment there, but is there a subdivision of the far left into which he should be grouped?
The most confusing label is moderate. As best I can determine, the press seems to apply that label to those who are willing to "compromise", to "reach across the aisle" and in general are more interested in being known as moderate than in actually having principles. If this analysis is correct, then one would expect them to, usually, go along with whichever group has the most votes. Any number of labels would be more accurate than moderate.
If it were up to me (and isn't that a scary thought!), there would be two labels. Those would be Constitutionalists and non-Constitutionalists, but the second would have to be subdivided, and here I think right and left would suffice. Constitutionalists would be those who believe in the Constitution and work to maintain the spirit of it; in particular, should they want to change it, they would do so by Amendment, as opposed to judicial fiat or word parsing. The left wing non-Constitutionalists would be those who think the Constitution leaves too much power to individuals and right wing non-Constitutionalists would likely feel it gave too much power to the government. If these labels were used, it would seem the media should call the Constitutionalists moderate, but I'm pretty sure they wouldn't.